4.3 MPI Limp home mode

[Carl]

Hi Guys ...
My mates boat (Monterey) has the 4.3 mpi v6 in and it keeps going into limp mode at the moment, sits at 3000 revs, won't go higher. ..

I've no idea how old the motor is or anything else ... ... any clues would be very much appreciated...

[Ianfs]

Have you got any more detailed information Carl?

I'm guessing its a Volvo engine?
Does it run normally and reach flat out revs 4,500-4,800 then stick at 3,000 after a period of time?
How long will it run before sticking to 3,000rpm?
Does it just stay at 3,000rpm regardless and not run any faster?
Why do you think its limp mode?

First thoughts might be incorrect voltages caused by corrosion, giving the ECM incorrect readings. Faulty injector codes again from unclean wiring/connectors, possibly ECM connectors.

I would advise plugging it in to get the fault codes, quickest route, after checking connectors/earth's etc.

[Carl]

will ask my mate ....

[Carl]

It's a Mercruiser ... and the Limp home mode is the same sort of thing you get in a car ....

[Ianfs]

And does it start up in limp mode or will it run normally for a while first?
It could be a number of things, an overheat problem, injectors, ECM, bad connections.
Unfortunately there's not much information to go on. I would advise getting a plug in to get the fault codes.

[_Ed_]

That needs code reading. The ecu will have the reason why stored in it.

[Carl]

He is getting it tested on a diagnostics thingy ..... will update once I know what's what.

[Ianfs]

Cheers Carl, its the best approach and the most cost effective.

[Gazjen]

Check the daft things first, mine goes into limp mode if oil pressure is low, water temp is high or drive oil is low although it also sounds the alarm